Reflectance measurement of macular pigment using multispectral imaging

Abstract

Imaging apparatus and filters are provided for accurately imaging, assessing and measuring a patient's macular pigment. A multi-band filter is employed in combination with a color digital fundus camera to provide a method that operates with a single imaging exposure. The multiband filter has bandpass regions within spectral ranges of the red, green and blue detectors of the CCD array employed within the fundus camera, the bandpass regions being sufficiently sharply defined so as to avoid regions where the CCD detector responses spectrally overlap. This provides three discrete channels of grayscale data corresponding to the bandpass regions of the multiband filter, which can be used to calculate macular pigment topographically. Methods are also disclosed for calculating the optical density of the macular pigment and advantageously displaying the resulting data.

1 . A filter, usable with a fundus camera, for imaging macular pigment in a patent, said multiband filter having at least two discrete bandpass regions, said at least two bandpass regions including a region centered near 465 nm and at least one other discrete bandpass region. 
     
     
         2 . A filter in accordance with  claim 1 , wherein said filter comprises a single filter element having at least two bandpass regions. 
     
     
         3 . A filter in accordance with  claim 1 , wherein said at least two discrete bandpass regions comprise three discrete bandpass regions centered near 465 nm, 535 nm and 630 nm, respectively. 
     
     
         4 . A filter in accordance with  claim 2  which has been manufactured by applying coatings by ion beam sputtering. 
     
     
         5 . A filter in accordance with  claim 2 , wherein unwanted wavelengths are blocked by about 5 OD or more.